In our testing so far, we found that the Crank (see image below) is the part of Stanley’s leg that is the easiest to break.
When the robot falls on its side, strong impacts on the tip of the crank are likely to occur, which causes it to snap.
As seen in the picture above the snap occurs across layer lines, so layer adhesion does not play a role here.
We took two preventive measures against this. First - we switched the material we use from PET-G to Polycarbonate.
Not only does Polycarbonate have a 40% higher tensile strength than PET-G, but its impact strength is an order of magnitude better, which makes it a perfect material for this demanding part.
The second improvement was the introduction of a TPU (Fiberlogy MatteFlex) bumper - to soften the impacts and prevent scratching. So far we haven’t seen this setup break, but we keep testing, and keep improving!